This disclosure is generally directed to imaging members, photoreceptors, photoconductors, and the like. More specifically, the present disclosure is directed to single layered flexible, belt imaging members, or devices comprised of an optional supporting medium like a substrate, and thereover a single layer comprised of a photogenerating pigment or pigments, a charge transport component or components, and a metal oxide having applied thereto a chelating agent of, for example, an anthraquinone like a tetrafluorodihydroxyanthraquinone, an optional adhesive layer, an optional hole blocking or undercoat layer, and an optional overcoating layer. In embodiments, there is selected as the photogenerating pigment a titanyl phthalocyanine or a hydroxygallium phthalocyanine prepared as illustrated herein, and where these pigments are stable especially in the presence of solvents, such as tetrahydrofuran (THF), which solvent is selected to provide for adequate specific component solubility in a binder present, such as a polycarbonate, and where charge leakage is reduced by the use of a suitable chelating agent. More specifically, there is selected in embodiments for the preparation of the photogenerating dispersion a mixture of THF and a halobenzene like monochlorobenzene.
In embodiments of the present disclosure there is selected as the photogenerating pigment a hydroxygallium phthalocyanine, especially hydroxygallium phthalocyanine Type V prepared, for example, as disclosed in U.S. Pat. No. 5,482,811, the disclosure of which is totally incorporated herein by reference, which comprises hydrolyzing a gallium phthalocyanine precursor pigment by dissolving the hydroxygallium phthalocyanine in a strong acid, and then reprecipitating the resulting dissolved pigment in basic aqueous media; removing any ionic species formed by washing with water; concentrating the resulting aqueous slurry comprised of water and hydroxygallium phthalocyanine to a wet cake; removing water from said slurry by azeotropic distillation with an organic solvent, and subjecting said resulting pigment slurry to mixing with the addition of a second solvent to cause the formation of said hydroxygallium phthalocyanine polymorphs. Also, the hydroxygallium phthalocyanine can be prepared as disclosed in U.S. Pat. No. 5,473,064, the disclosure of which is totally incorporated herein by reference, whereby a pigment precursor Type I chlorogallium phthalocyanine is prepared by reaction of gallium chloride in a solvent, such as N-methylpyrrolidone, present in an amount of from about 10 parts to about 100 parts, and more specifically, about 19 parts with 1,3-diiminoisoindolene (DI3) in an amount of from about 1 part to about 10 parts, and more specifically, about 4 parts of DI3, for each part of gallium chloride that is reacted; hydrolyzing said pigment precursor chlorogallium phthalocyanine Type I by standard methods, for example acid pasting, whereby the pigment precursor is dissolved in concentrated sulfuric acid, and then reprecipitated in a solvent, such as water, or a dilute ammonia solution, for example from about 10 to about 15 percent; and subsequently treating the resulting hydrolyzed pigment hydroxygallium phthalocyanine Type I with a solvent, such as N,N-dimethylformamide, present in an amount of from about 1 volume part to about 50 volume parts, and preferably about 15 volume parts for each weight part of pigment hydroxygallium phthalocyanine that is used by, for example, ball milling the Type I hydroxygallium phthalocyanine pigment in the presence of spherical glass beads, approximately 1 millimeter to 5 millimeters in diameter, at room temperature, about 25° C., for a period of from about 12 hours to about 1 week, and more specifically, about 24 hours.
More specifically, a preparation process for obtaining Type V hydroxygallium phthalocyanine comprises the formation of a precursor gallium phthalocyanine with, for example, an X-ray powder diffraction trace having peaks at Bragg angles of 7.6, 8.1, 9.7, 16.0, 18.4, 19.2, 19.9, 24.7, 25.7 and 26.2, and the highest peak at 8.1 degrees 2θ, prepared by the reaction of 1,3-diiminoisoindolene with gallium acetylacetonate in a suitable solvent, such as N-methylpyrrolidone, or halonaphthalene like 1-chloronaphthalene, quinoline, and the like; hydrolyzing the precursor by dissolving in a strong acid and then reprecipitating the resulting dissolved pigment in aqueous ammonia, thereby forming Type I hydroxygallium phthalocyanine; and admixing the Type I formed with a hydrophobic solvent of, for example, hexanes, including 1-hexanes and/or isomers thereof, heptane, cyclohexane, cyclopentane or esters, such as propylacetate, butylacetate, or ketones, such as methyl isobutyl ketone, methyl isoamyl ketone, or toluene, and thereafter azeotropically removing water therefrom. Yet more specifically, the process comprises the formation of a precursor prepared by the reaction of 1 part gallium acetylacetonate with from about 1 part to about 10 parts, and more specifically, about 4 parts 1,3-diimiinoisoindolene in a solvent, such as quinoline, chloronaphthalene, or N-methylpyrrolidone, in an amount of from about 10 parts to about 100 parts, and more specifically, about 19 parts, for each part of gallium acetylacetonate that is used, to provide a pigment precursor gallium phthalocyanine, which is subsequently washed with a component, such as dimethylformamide to provide the precursor gallium phthalocyanine as determined by X-ray powder diffraction with an X-ray powder diffraction trace having peaks at Bragg angles of 7.6, 8.1, 9.7, 16.0, 18.4, 19.2, 19.9, 24.7, 25.7, and 26.2, and the highest peak at 8.1 degrees 2θ; dissolving 1 weight part of the resulting gallium phthalocyanine in concentrated, about 94 percent, sulfuric acid in an amount of from about 1 weight part to about 100 weight parts, and in an embodiment about 5 weight parts, by stirring the pigment precursor gallium phthalocyanine in the acid for an effective period of time, from about 30 seconds to about 24 hours, and in an embodiment about 2 hours at a temperature of from about 0° C. to about 75° C., and more specifically, about 40° C., in air or under an inert atmosphere, such as argon or nitrogen; adding the resulting mixture to a stirred organic solvent in a dropwise manner at a rate of about 0.5 milliliter per minute to about 10 milliliters per minute, and in an embodiment about 1 milliliter per minute to a nonsolvent, which can be a mixture comprised of from about 1 volume part to about 10 volume parts and more specifically, about 4 volume parts of concentrated aqueous ammonia solution (14.8N), and from about 1 volume part to about 10 volume parts, and more specifically, about 7 volume parts of water for each volume part of acid like sulfuric acid that was used, which solvent mixture was chilled to a temperature of from about −25° C. to about 10° C., and in an embodiment about −5° C. while being stirred at a rate sufficient to create a vortex extending to the bottom of the flask containing the solvent mixture; isolating the resulting blue pigment by, for example, filtration; and washing the hydroxygallium phthalocyanine product obtained with deionized water by redispersing and filtering from portions of deionized water, which portions are from about 10 volume parts to about 400 volume parts, and in an embodiment about 200 volume parts for each weight part of precursor pigment gallium phthalocyanine which was used. The product, a dark blue solid, was confirmed to be Type I hydroxygallium phthalocyanine on the basis of its X-ray diffraction pattern having major peaks at 6.9, 13.1, 16.4, 21.0, 26.4, and the highest peak at 6.9 degrees 2θ. The Type I hydroxygallium phthalocyanine product obtained as a wet cake, approximately 10 percent by weight pigment and 90 percent by weight water, can then be dried by azeotropically distilling off water with a hydrophobic solvent, such as hexane, of from 1 part to 30 parts of wet cake to 100 parts by volume of solvent, more specifically, 20 parts. Water is removed by heating to the azeotrope boiling point and continued until the distillate temperature reaches the boiling point of the hydrophobic solvent. The advantages of this method are, for example, that drying of the pigment consumes from 1 to 5 hours versus, for example, greater than 24 hours under vacuum by conventional means. Furthermore, the particle size remains in the range of about 150 to about 300 nanometers as measured by TEM. Also, in embodiments the obtained crude hydroxy gallium phthalocyanine can be washed to reduce the sulfur content. The sulfur reduction washes can be accomplished on either the Type I hydroxygallium phthalocyanine or on the Type V hydroxy gallium phthalocyanine product. In the situation with sulfur reduction of the Type I hydroxygallium phthalocyanine, 1 part pigment to 10 parts pigment, more specifically, 5 parts pigment are redispersed in a hydrophilic solvent of, for example, N-methylpyrrolidone, tetrahydrofuran, acetone, methanol, isopropanol and N—N-dimethylformamide, from 100 parts solvent to 1,000 parts solvent, and more specifically, 300 parts. Subsequently, concentrated ammonium hydroxide (38 percent NH4OH) solution is added, from 50 parts to 600 parts, and more specifically, 100 parts. The resulting dispersion is stirred for from 1 minute to 24 hours, and more specifically, 2 hours, and then filtered through a ceramic Buchner funnel using GFF/F filter paper. The organic solvent/aqueous base washing is repeated 1 to 4 times, and more specifically, 1, and then the Type I hydroxygallium phthalocyanine is washed with deionized water until the filtrate conductivity is below from about 0.1 to about 20 milliSiemens per centimeter squared. The wet Type I hydroxygallium phthalocyanine pigment can than be dried azeotropically, and then converted to Type V hydroxygallium phthalocyanine by stirring in the solvent N,N-dimethylformamide 1 part Type I pigment to 15 parts solvent.
The hydroxygallium photogenerating pigment essentially free of chlorine can also be can be prepared by the conversion of Type I hydroxygallium phthalocyanine to Type V hydroxygallium phthalocyanine wherein the Type I hydroxygallium phthalocyanine is prepared by the hydrolysis of the dimer 1,2-di(oxogallium phthalocyaninyl)ethane. The preparation of the dimer includes, for example, the dissolution of a suitable amount, such as about 1 part gallium chloride in a suitable amount of, for example, about 5 parts to about 15 parts of toluene at a suitable temperature of, for example, from about 20° C. to about 30° C. to form a solution of gallium chloride. Subsequently, the resulting gallium chloride solution is contacted with a suitable amount of, for example, from about 2 parts to about 4 parts of an alkali alkoxide like sodium methoxide at a suitable temperature of, for example, from about 20° C. to about 40° C. to form a gallium alkoxide like gallium methoxide. The gallium methoxide solution can then be contacted with a suitable amount of, for example, from about 2 parts to about 6 parts of a dicyano benzene selected in a suitable amount, such as for example, from about 5 parts to about 15 parts, of an alkylene glycol like ethylene glycol for each part of gallium methoxide formed. The reaction mixture is then heated at a suitable temperature of, for example, from about 185° C. to about 205° C. for a suitable period of, for example, from about 1 hour to about 3 hours to provide the alkoxy-bridged gallium phthalocyanine dimer pigment precursor 1,2-di(oxogallium phthalocyaninyl)ethane. The formed dimer precursor is then stirred for a suitable time period, such as for example from about 1 to about 3, and more specifically, about 2 hours, in an acid like sulfuric acid present in a suitable amount, such as for example, from about 25 weight parts to about 75 weight parts, and retaining the temperature of the solution at, for example, from about 40° C. to about 60° C. in air or under an inert atmosphere such as argon or nitrogen. The resulting pigment slurry is then acid pasted into an aqueous base solution like ammonium hydroxide selected in a suitable amount, such as for example, from about 50 to 100 weight parts, of ammonium hydroxide.
A mixed solvent system may be utilized to convert Type I HOGaPc to Type V HOGaPc, and which allows for a controlled conversion of Type I HOGaPc to Type V HOGaPc thereby yielding a more uniform Type V HOGaPc pigment with a preselected particle diameter size. The solvent system may include at least two of a polar aprotic solvent, an ester and/or a ketone solvent mixture. Suitable polar aprotic solvent, such as N,N-dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, acetonitril, and mixtures thereof, in combination with an ester, such as n-butyl acetate, ethyl acetate, and mixtures thereof and/or a ketone such as acetone, methyl ethyl ketone, methyl isobutyl ketone, combinations thereof, and the like. The resulting Type V HOGaPc possesses an X-ray diffraction pattern having major peaks at Bragg angles of 7.4, 10, 12.2, 16.8, 18.6, 24, 25.3, 26.8, 28.3, 32, 2θ (2θ±0.2°).